Owls are nocturnal birds. There were many owls in Narnia, some of which were talking owls.
Upon the creation of Narnia, owls were one of the many species chosen to become talking animals. They were noted for their wisdom and careful demeanor. One of the first talking owls was chosen to sit at the First Council by Aslan.
Over the centuries, they established the Parliament of Owls, an organization of talking owls that meets at night to help avert trouble in Narnia. They did this because, being nocturnal, they could rarely be involved in most important meetings that took place during the most unnatural and inconvenient time: day.
Like all talking beasts, owls resembled their non-sentient counterparts, although far different in size. Talking owls were about twice large as the largest owls of our world, around 4-5 feet, as tall as a human adolescent. This gave them a wingspan of approximately twelve feet.
Their size did not hamper their ability to fly, being as agile as their smaller counterparts. Being so much larger, talking owls could carry significant weights. In The Silver Chair, owls are seen carrying human beings on their backs.
Like regular owls, talking owls were carnivorous, feeding on small, nocturnal beasts (not talking beasts, of course). One of their favorite treats were nocturnal bats, which they could swoop down on and gobble up in one bite.